Toughened benzocyclobutene based polymers and their use in building-up printed wiring boards

ABSTRACT

The invention is a process for building-up printed wiring boards using metal foil coated with toughened benzocyclobutene-based dielectric polymers. The invention is also a toughened dielectric polymer comprising benzocyclobutene-based monomers or oligomers, ethylenically unsaturated polymer additive, and, optionally, a photoactive compound.

This application is a Divisional of U.S. application Ser. No.09/496,495, filed Feb. 2, 2000 now U.S. Pat. No. 6,420,093.

This invention was made with Government support under Agreement No.MDA972-95-3-0042 awarded by ARPA. The Government has certain rights inthe invention.

FIELD OF THE INVENTION

This invention relates to a process for making additional interconnectlayers on commercially available printed circuit boards using toughenedbenzocyclobutene based polymers and metal foils coated with suchpolymers. This invention also relates to such toughenedbenzocyclobutene-based polymers.

BACKGROUND OF THE INVENTION

Various printed wiring boards or printed circuit boards (referred toherein as “PWBs”) are known and frequently have two to eight layers oflaminates. Occasionally, it is desirable to add additional layers tothese board structures (see, e.g., H. T. Holden, In Printed CircuitsHandbook, 4^(th) ed., C. F. Coombs, Jr., Ed.; McGraw-Hall: New York,1996, Chapter 4). For high frequency applications, the insulatingmaterials typically used in the PWBs (e.g., epoxy materials) may notprovide the desired low dielectric loss. Therefore, it would bedesirable to have a process and materials which could provide thedesired low dielectric loss.

Benzocyclobutene-based polymers (hereinafter referred to as “BCBpolymers”) are thermosetting polymers. Certain of these polymers havelow dielectric constants and thus, are desirable as insulating coatingsin various electronics applications (see, e.g., “Benzocyclobutene(BCB)Dielectrics for the Fabrication of High Density, Thin Film MultichipModule,” Journal of Electronics Materials, Vol. 19, No.12, 1990 and G.Czornyl, M. Asano, R. L. Beliveau, P. Garrou, H. Hiramoto, A. Ikeda, J.A. Kreuz and O. Rohde, In Microelectronic Packaging Handbook, Volume 2;R. R,.Tummala, E. J. Rymaszewski and A. G. Klopfenstein, Eds.; Chapman &Hall: New York, 1997; Chapter 11). However, for certain applications,BCB polymers may not have sufficient toughness. Therefore, it would bedesirable to have a BCB polymer with increased toughness withoutsignificant loss or degradation of other desirable properties.

JP 8-60103 discloses an adhesive sheet comprises a compound having abenzocyclobutene group and a binder polymer. The preferred binderpolymers have carbon-carbon unsaturated bonds. The reference indicatesthat from about 1-95 percent of the composition may be the binderpolymer.

SUMMARY OF THE INVENTION

According to a first embodiment, the present invention is a processcomprising

providing a printed wiring core board, which comprises a glass fiberreinforced board with conductive metal circuitry,

laminating to the printed wiring core board a sheet comprising a foil ofa conductive metal and, on the foil, a dielectric layer of a curablecomposition comprising (a) at least one precursor compound selected fromarylcyclobutene monomers, arylcyclobutene oligomers, and combinationsthereof; and (b) a polymer or oligomer having a backbone comprisingethylenic unsaturation (i.e., carbon-to-carbon double bond(s)), wherein,during the lamination step, the dielectric layer is in contact with theprinted wiring board, and

processing the laminated article to form additional electricalconnections.

According to a second embodiment, this invention is a preferredcomposition comprising

a) at least one precursor compound selected from arylcyclobutenemonomers, arylcyclobutene oligomers, and combinations thereof; and

b) a polymer or oligomer having a backbone comprising ethylenicunsaturation (i.e., carbon-to-carbon double bond(s)) and terminalacrylate or methacrylate groups. The invention is also the partiallypolymerized (b-staged) reaction product of this composition and thecured reaction product of the b-staged material.

According to yet a third embodiment, the invention is a sheet comprisinga metal foil and a film comprising the composition of the secondembodiment or the partially cured product of that composition.

DETAILED DESCRIPTION OF THE INVENTION

The core board to which the BCB coated metal foil is laminated ischaracterized by having various insulating layers laminated together andseparating various metal interconnect lines. Processes for making suchPWBs are well-known (see, e.g., Printed Circuits Handbook, 4^(th) Ed.,C. F. Coombs, Jr., McGrall-Hill: New York, 1996). Typically, theinsulating layers are glass reinforced epoxy. The metal foil is a verythin layer of a conducting metal, such as Cu or Cu alloy, and ispreferably copper. The thickness of the metal foil is preferably about 3to 50 microns. The BCB dielectric layer is preferably coated from asolvent onto foil. Suitable solvents include mesitylene xylenes,toluene, methyl ethyl ketone, cyclic ketones and a mixture of thesesolvents. After coating, the composition is preferably baked attemperatures from 100° C. to 200° C., more preferably 120° C. to 180° C.in air for 5 to 30 minutes, most preferably at 140° C. to 160° C. for 10to 20 minutes.

Lamination to the core board may occur according to standard processes,preferably by vacuum hot press at temperatures of 200° C.-250° C. andpressures of 10-40 Kg/cm².

Additional patterning steps may then be performed to the laminateaccording to known procedures. For example, the metal foil could bestripped or pattern etched followed by via formation with a laserdrilling (e.g. with a CO₂ laser), or the entire laminate could bemechanically drilled through. Electroless plating of additionalconductive metal, such as copper, followed by electroplating (e.g. withcopper) could be used to form the desired electrical connections.

As stated above, the precursor is either an arylcyclobutene monomer, ab-staged oligomer of one or more arycyclobutene monomers, or somecombination of b-staged arylcyclobutene oligomers and/or monomers.

Preferably, the monomers are of the formula

wherein

B¹ is an n-valent organic linking group, preferably comprising ethylenicunsaturation, or B¹ is absent. Suitable single valent B¹ groupspreferably have the formula —CR⁸═CR⁹Z, wherein R⁸ and R⁹ areindependently selected from hydrogen, alkyl groups of 1 to 6, mostpreferably 1 to 3 carbon atoms, and aryl groups, and Z is selected fromhydrogen, alkyl groups of 1 to 6 carbon atoms, aryl groups, —CO₂R⁷wherein R⁷ is an alkyl group, preferably up to 6 carbon atoms, an arylgroup, an aralkyl group, or an alkaryl group. Most preferably Z is—CO₂R⁷ wherein R⁷ is an alkyl group, preferably up to 6 carbon atoms, anaryl group, an aralkyl group, or an alkaryl group. Suitable divalent B¹groups include —(CR⁸═CR⁹)_(o)—(Z′)_(o−1), wherein R⁸ and R⁹ are asdefined previously, o is 1 or 2, and Z′ is an alkyl group of 1 to 6carbon atoms, an aromatic group, or a siloxane group. Most preferably ois 2 and Z′ is a siloxane group.

Ar¹ is a polyvalent aromatic or heteroaromatic group and the carbonatoms of the cyclobutane ring are bonded to adjacent carbon atoms on thesame aromatic ring of Ar¹, preferably Ar¹ is a single aromatic ring;

m is an integer of 1 or more, preferably 1;

n is an integer of 1 or more, preferably 2-4, more preferably 2; and

R¹ is a monovalent group, preferably hydrogen, lower alkyl of up to 6carbon atoms.

The synthesis and properties of these cyclobutarenes, as well as termsused to describe them, may be found, for example, in U.S. Pat. Nos.4,540,763; 4,724,260; 4,783,514; 4,812,588; 4,826,997; 4,999,499;5,136,069; 5,185,391; 5,243,068, all of which are incorporated herein byreference.

According to one preferred embodiment, the monomer (a) has the formula

wherein

each R³ is independently an alkyl group of 1-6 carbon atoms,trimethylsilyl, methoxy or chloro; preferably R³ is hydrogen;

each R⁴ is independently a divalent, ethylenically unsaturated organicgroup, preferably an alkenyl of 1 to 6carbons, most preferably—CH₂═CH₂—;

each R⁵ is independently hydrogen, an alkyl group of 1 to 6 carbonatoms, cycloalkyl, aralkyl or phenyl; preferably R⁵ is methyl;

each R⁶ is independently hydrogen, alkyl of 1 to 6 carbon atoms, chloroor cyano, preferably hydrogen;

n is an integer of 1 or more;

and each q is an integer of 0 to 3.

The preferred organosiloxane bridged bisbenzocyclobutene monomers can beprepared by methods disclosed, for example, in U.S. Pat. Nos. 4,812,588;5,136,069; 5,138,081 and WO 94/25903. The preferred compound where n is1, q is 0, R⁴ is —C═C—, R⁵ is methyl, and R⁶ is hydrogen is referred toherein as DVS-bisBCB.

If an oligomeric precursor is desired, the BCB monomers may be b-stagedaccording to any known process. The monomers may be partiallypolymerized or b-staged neat (i.e., without solvent) by heating (see,e.g., U.S. application Ser. No. 08/290,197 and U.S. Pat. No. 4,642,329,incorporated herein by reference). Alternatively, the monomers may bepartially polymerized or b-staged in a solvent (see, e.g., U.S.application Ser. No. 08/290,197, incorporated herein by reference). Whenoligomeric precursors are used, the weight average molecular weight (Mw)is preferably less than 200,000, more preferably less than 150,000 andpreferably greater than 10,000, more preferably greater than 20,000.

The second component having the ethylenic unsaturation in the carbonbackbone should be selected so that it can withstand the processingconditions (solvents, heating, etc.) used in microelectronicsfabrication and not cause a significant deterioration in the electricalinsulating properties of the reaction product relative to an unmodifiedBCB polymer. Suitable materials include polymers based on butadiene,isoprene, ethylene-butene, and ethylene-propylene. Comonomeric units,such as styrene and methylstyrene, may also be used. Preferably, theethylenically unsaturated polymer is selected from polybutadiene,polyisoprene, styrene-butadiene block copolymers, and styrene-isopreneblock copolymers. Applicants have found that the terminal groups on theethylenically unsaturated polymer can have a profound effect on theperformance of the composition. Acrylate or methacrylate terminatedpolymers are the preferred materials, as recited in the secondembodiment of this invention, with acrylate terminated polybutadienesbeing the more preferred. The most preferred polymer has the formula

wherein l, m and n represent the mole fraction of the respective groupin the polymer and (l+n) is from about 0.4 to about 0.95 and m is fromabout 0.05 to about 0.6, R and R′ are independently in each occurrencealkyl groups of 1 to about 10 carbon atoms, and preferably are methylgroups.

The molecular weight (Mw) of the second component is preferably lessthan 150,000, more preferably less than 100,000, most preferably lessthan 80,000, and preferably greater than 3,000, more preferably greaterthan 5,000.

The amount of the second component used in the composition should besuch as to avoid excessive phase separation between the first and secondcomponents. When phase separation occurs significantly, it depends uponvarious factors, such as the molecular weights of the components, thecharacteristics and relative amounts of any comonomers, the solventsused, and the temperature of processing. Preferably, the amount of thesecond component is less than 50 parts per hundred parts of thearylcyclobutene material (phr). For the composition of the secondembodiment (the preferred composition having acrylate terminal groups),the second component is preferably present in amounts of at least 20 phrto give the maximum combination of toughness, flexibility anddimensional stability. For other non-preferred embodiments, the amountof the second component is preferably less than 15 phr to avoid phaseseparation and solubility problems.

The composition may be cured by any known method, such as, for example,by heating to temperatures from 200° C. to 300° C. Frequently, thecomposition is coated on a substrate (e.g., by spin coating, or drawingwith a bar) to yield a film, and dried and cured by heating.

If desired, a photosensitive compound may be added to render thecomposition photosensitive. A coated film of the composition can then bepatterned by exposure to activating wavelengths of radiation.Photosensitizers that increase the photoactive compound'sphotosensitivity may also be added. Any photoactive compounds andphotosensitizers that are known in the art may be used. Examples ofphotoactive compounds include bisazides, a combination of bismaleimides,acrylates, acetylenes, and radical initators such as2,2-dimethoxy-2-phenylacetophenone. The amount of photoactive compoundis preferably 0.1 percent to 20 percent by weight, more preferably about0.5 percent to 8 percent, based on total weight of components a and band the photoactive compound. See U.S. application Ser. No. 08/290,197,incorporated herein by reference, for additional discussion regardingphotocurable BCB compositions and methods of developing suchcompositions. See also U.S. Ser. No. 09/177,819, incorporated herein byreference.

Flame retardant compounds may be added to render the flame retardancy.Examples of flame retardant compounds include phosphate compounds, suchas triphenylphosphate and trishaloethyl phosphate, halogenatedcompounds, such as polymerized tetrabromo-bis-phenol A and inorganiccompounds such as magnesium and calcium carbonate. Multiple flameretardant compounds can be used to enhance the flame retardant effect.The amount of flame retardant compound is preferably 5 percent to 20percent by weight, more preferably about 5 percent to 10 percent, basedon total weight of components a and b and the photoactive compound.

Other components, such as antioxidants (e.g., quinolines, hinderedamines, monomethyl ether hydroquinone, and2,6-di-tert-butyl-4-methylphenol), adhesion promoters, additionalcross-linkers (e.g., 2,6-bis(4-azidobenzylidene)-4-ethylcyclohexanone)(BAC-E) that are known in the art may also be included in thecomposition. Using additional cross-linkers that are reactive to BCBunder dry, heated conditions are advantageous for the metal-coated foilsbecause they enable one to control resin flow during the laminationprocess.

Suitable solvents for the composition include mesitylene, xylenes,toluene, methyl ethyl ketone, cyclic ketones and mixture of these.

EXAMPLES

Structures and information of polystyrene-polybutadiene-polystyrene(SBS) triblock copolymer (VECTOR from Dexco), dihydroxyl terminatedpolybutadiene (R45HT from Elf-Atochem) and diacrylate terminatedpolybutadiene (BAC-45 from Osaka Organic Chemical Industry, Inc.) usedin some of the examples are listed below:

VECTOR 8505: styrene/diene ratio=29/71; Mw ca 75,000 g/mol.

VECTOR 6241: styrene/diene ratio=43/57; Mw ca 62,000 g/mol.

(l+n)=95 to 50 percent

m=5 to 50 percent

R45HT:

Mw ca. 6,200 g/mol.; Mn ca. 2,800 g/mol.

BAC-45:

Mw ca. 6,600 g/mol; Mn ca. 3,000 g/mol

Example 1

The ethylenically unsaturated elastomers listed below were evaluated fortheir usefulness in modifying formulations comprising benzocyclobuteneoligomers:

TABLE I Liquid Polybutadiene Manufacturer Product Name Chemistry Mn Cis& Trans % Japan B-700 Allyl  700   30% Petrochemical B-1000 terminated1000 B-2000 polybutadiene 2000 B-3000 3000 Huls POLYOIL 110 3000   99%Idemitsu POLY BD Hydroxy 2900 80 R45HT Petrochemical POLY BD terminated1200 80 R15HT polybutadiene Osaka Organic BAC-45 Methacrylate 2900 80Chemical terminated polybutadiene

TABLE II SBS Elastomer Styrene/Diene Manufacturer Product Name Mw RatioDexco VECTOR 6030 145,000 30/70 VECTOR 2518 100,000 31/69 VECTOR 8508 75,000 29/71 VECTOR 6241  62,000 43/57

The compatibility of these materials in a polymer based on theDVS-bisBCB monomer is shown in the following table:

TABLE III Compatibility of Elastomer to BCB Maximum Solubility to 50%Add-in Level BCB Polymer Without Bleedout (Mw = 140,000) Phenomena bySolution in Thermal Cure Manufacturer Product Name Mesitylene ProcessJapan B-700 >30 phr 15 Phr Petrochemcal B-1000 >30 15 B-2000 >30 10B-3000 >30 <10 Huls POLYOIL 110 >30 10 Idemitsu POLY BD >30 10 R45HTPetrochemical POLY BD 10 15 R15HT Osaka Organic BAC-45 >30 >30 ChemicalDexco VECTOR 6030 <4 phr — VECTOR 2518 <4 phr — VECTOR 8508 5 phr >20phr VECTOR 6241 10 phr >20 phr

The various elastomers in combination with the BCB polymer were furtherevaluated for tackiness, amount of curl experienced when coated onto acopper foil and for bend flexibility of the coated copper foil as shownbelow:

TABLE IV B-Stage Polymer Film Evaluation Bend Add-in Flexibility Levelto Tackiness (Bending Mw140K and Cu Radius at Manufacturer Product NameBCB Foil Curl Cracking) Japan B-700 15 Phr OK R = 20 mm PetrochemcalB-1000 15 Phr OK R = 20 mm B-2000 10 Phr OK R = 20 mm B-3000 5 Phr OK R= 50 mm Huls POLYOIL 110 10 Phr OK R = 10 mm Idemitsu POLY BD 10 Phr OKR = 10 mm R45HT Petrochemical POLY BD 10 Phr OK R = 10 mm R15HT OsakaOrganic BAE-45 20 Phr OK  R = 0.5 mm Chemical Dexco VECTOR 8508 5 PhrCurl  R > 100 mm VECTOR 6241 10 Phr Curl  R > 100 mm Dow BCB monomer 20Phr OK R = 20 mm

The coated copper foils were then cured or C-staged and furtherevaluation of toughness of the cured composition occurred as shownbelow:

TABLE V C-Stage Polymer Film Evaluation Add-in Level Knife Scribe toMw140K Test Manufacturer Product Name BCB (Toughness) * Japan B-700 15Phr 1 Petrochemcal B-1000 15 Phr 1 B-2000 10 Phr 1 B-3000 5 Phr 1 HulsPOLYOIL 110 10 Phr 3 Idemitsu POLY BD 10 Phr 3 R45HT Petrochemical POLYBD 10 Phr 3 R15HT Osaka Organic BAC-45 20 Phr 5 Chemical Dexco VECTOR8508 5 Phr 3 VECTOR 6241 10 Phr 3 DOW BCB monomer 20 phr 1 * Rating: 1poor-5 excellent

Example 2 Polymer Coated Cu Foil with 15% BAC-45 in Mw of 140,000 g/mol.BCB

Eighty weight parts of B-staged BCB (Mw=140,000 g/mol.), 15 weight partsof BAC-45, and 1 part of bis-azide cross-linker were blended in 100parts of mesitylene. The solution was clear. The solution was coated onthe matte side of a 0.5 oz. Cu foil with a doctor blade that had a 200μm gap between the blade and the Cu foil surface so that the thicknessof the dry-up BCB film was 100 μm. After coating, the polymer coated Cufoil was placed in a 150° C. oven for 15 minutes to evaporate thesolvent. The B-stage polymer coated Cu foil was not coiled, and itgenerated no cracks in the bending test with 10 mm diameter cylindricalspacer.

The B-stage polymer coated Cu foil was laid up on a 1.6 mm thick and 30cm×30 cm FR-4 laminate board whose Cu circuit had black oxide surface.The set was placed in a vacuum hot press machine. The hot press wasprogrammed so that temperature was ramped at 5° C. per minute to 210° C.and was kept for 3 hours. The hot press pressure was maintained at 10Kg/cm² until the temperature went-up to 170° C. and then was increasedto 30 Kg/cm² and maintained until the press program finished. Thepost-press thickened polymer layer built on FR-4 core board was approx.80 μm+/−10 μm. The board was cut into 1 inch by 4 inch strips for Cufoil peel strength measurement. The Cu peel strength was approximately1.0 Kg/cm and no BCB delamination from core board was observed.

Also, the board was cut into 2 inch by 2 inch pieces and the pieces wereplaced under a pressure cooker test (121° C. for 3 hours) and thendipped in a 260° C. solder bath for 1 minute. No blister was observed.

Example 3 Polymer Coated Cu Foil with 5% BAC-45 and 10% BCB Monomer inMw of 140,000 g/mol. BCB

Ninety weight parts of B-stage BCB (Mw=140,000 g/mol.), 5 weight partsof BAC-45, 5 weight parts of BCB monomer and 1 part of bis-azidecross-linker were blended in 100 parts of mesitylene. The solution wasclear. The polymer solution was coated on a Cu foil and thermally driedin the same manner as Example 2. Then, the polymer coated Cu foil waslaminated in the same manner as Example 2.

The post-press thickness polymer layer built on FR-4 core board was 80μm+/−10 μm. The board was cut into 1 inch by 4 inch strips for Cu foilpeel strength measurement. The Cu peel strength was approximately 0.9Kg/cm² and no BCB delamination from core board was observed. Also, theboard was cut into 2 inch by 2 inch pieces and the pieces were placed ina pressure cooker test (121° C. for 3 hours) and then dipped in a 260°C. solder bath for 1 minute. No blister was observed.

Example 4 Flexible Metalized Sheet with 30% BAC-45 in Mw of 140,000g/mol. BCB

Seventy weight parts of B-stage BCB (Mw=140,000 g/mol.), 30 weight partsof BAC-45 and 3 parts of bis-azide cross-linker were blended in 100parts of mesitylene. The solution was clear. The polymer-coated solutionwas coated on the shiny side of a {fraction (1/4 )}oz. Cu foil andthermally dried in the same manner as Example 2. The coating thicknesswas 100 μm. Then, polished stainless steel plate was laid upon thepolymer side of the polymer coated Cu foil, and hot-pressed in the samemanner as Example 2. After the hot press process, the polymer coated Cufoil was peeled off from the stainless steel plate. The post-pressedpolymer layer thickness was 100 μm. The polymer sheet was subjected tobending test with 1 mm thick spacer. No crack occurred.

Example 5 Glass Reinforced Substrate with 15% BAC-45 in Mw of 140,000g/mol. BCB

Eighty weight parts of B-stage BCB (Mw=140,000 g/mol.), 15 weight partsof BAC-45, and 1 part of bis-azide cross-linker were blended in 120parts of mesitylene. The solution was clear. The polymer solution wascoated on and impregnated into a glass mat (Ohji Paper's Glassper)GMC-50E, thickness=380 μm) which was thermally dried at 150° C. for 30minutes to make a prepreg. The resin content of the prepreg wasapproximately 90 percent. Three sheets of the prepreg were laid-up andCu foil sheets were placed on top and bottom. Then, the set of prepregsheets and 0.5 oz. Cu foil sheets were placed in a vacuum hot press. Thehot press was programmed so that the temperature was ramped at 5°C./minute to 250° C. and was kept for 3 hours. The hot press pressurewas maintained at 10 Kg/cm² until the temperature went up to 170° C. andthen was increased to 30 Kg/cm² and maintained until the press programwas finished. The post-hot press thickness was 1.1+/−0.01 mm. The boardwas cut into 1 inch by 4 inch strips for Cu foil peel strengthmeasurement. The Cu peel strength was approximately 0.9 Kg/cm² and noBCB delamination from core board was observed.

The board was cut into 2 inch by 2 inch pieces and the pieces wereplaced under a pressure cooker test (121° C. for 3 hours) and thendipped in a 260° C. solder bath for 1 minute. No blister was observed.

Example 6 Preparation of 10% R45HT (Hydroxy Terminated Polybutadiene) inB-Staged BCB with Mw of 140,000 g/mol.

Five hundred grams of 51.2% BCB in mesitylene solution was mixed with28.5 grams of R45HT. One hundred grams of the above solution werediluted with 11.4 grams of mesitylene to generate a solution with 43.5%BCB and 4.84% R45HT. The solution was spin-coated on a 6 inch Cu coatedwafer at 3000 rpm. Cure program was from RT to 150° C. in 30 minutes, at150° C. for 20 minutes, from 150 to 250° C. in 40 minutes and at 250° C.for 1 hour. The film surface had a “scale” pattern which could be due tomigration of R45HT to the surface during cure. The coefficient ofthermal expansion (CTE) of a free-standing film is 94 ppm/° C.

Example 7 Preparation of 10% BAC-45 (Acrylate Terminated Polybutadiene)in B-Staged DVS-bisBCB (BCB) with Mw of 140,000 g/mol.

One hundred grams of 51.2% BCB in mesitylene was mixed with 5.8 g ofBAC-45 and 7 grams of mesitylene. The solution contained 45.5% BCB and5.14% BAC-45. A film was spin-coated and curved as in Example 6. Thesurface of the film was smooth. A portion of the film was freed from thewafer by etching off the copper with a 10% ammonium persulfate solution.Examination of the free-standing film by transmission electronmicroscopy (TEM) did not show any discrete domains. CTE of afree-standing film is 80 ppm/μC.

Example 8 Preparation of 20% BAC-45 in B-Staged DVS-bisBCB (BCB) with Mwof 140,000 g/mol.

One hundred and thirty-three grams of 51.2% BCB in mesitylene was mixedwith 17.1 grams of BAC-45 and 15 grams of mesitylene. The solutioncontained 41.3% BCB and 10.4% BAC-45. A film was spin-coated and curedas in Example 6. The surface of the film was smooth.

Example 9 Thin Film from 10% VECTOR 6241 in B-Staged DVS-bisBCB (BCB)with Mw of 140,000 g/mol.

Fifty grams of 51.2% BCB in mesitylene was mixed with 2.85 grams ofVECTOR 8508 and 3 grams of mesitylene. The solution contained 46.0% BCBand 5.1% VECTOR 6241. A film was spin-coated on a 6 inch copper coatedwafer at 4000 rpm and cured. The surface of the film was smooth. Afree-standing film was generated as in Example 7. Examination of thefree-standing film by transmission electron microphotography (TEM)showed domains of about 0.2 μm diameter.

Example 10 Thin Film from 3.9% VECTOR 8508 in B-Staged DVS-bisBCB (BCB)with Mw of 140,000 g/mol.

Seven hundred and fifty grams of 50.9% BCB in mesitylene was mixed with15.3 grams of VECTOR 8508 and 60 grams of toluene. The solution wasspin-coated on a 4 inch copper coated wafer at 2500 rpm. A free-standingfilm was examined by TEM and the domains of about 0.2 μm diameter wereobserved.

Example 11 Patterning Thin Film of BCB with 10% BAC-45

To 15 grams of CYCLOTENE (trademark of The Dow Chemical Co.), 4026-46dielectric was added 0.77 grams of BAC-45. A 0.3 weight percentpartially hydrolyzed vinyl triacetate silane solution was applied to a 4inch silicone wafer as adhesion promoter. The CYCOTENE 4026 solutionwith BAC-45 was spread at 500 rpm followed by spin-coating at 2700 rpmfor 30 seconds. The wafer was prebaked at 85° C. for 90 seconds on a hotplate. A Karl Suss photo exposure tool was used with the gap between thewafer and the mask to be 10 μm. Exposure dose was 600 mJ/cm².Predevelopment bake was 50° C. for 30 seconds. The wafer was puddledeveloped with DS-2100, which is a mixture of PROGLYDE DMM (dipropyleneglycol dimethyl ether from The Dow Chemical Co.) and Isopar L (fromExxon). The development time was 22 seconds. The wafer was cured andthen treated with plasma. Final film thickness was 10.9 μm. All 75 μmvias were open.

Example 12 Patterning Thin Film of BCB with 10% R45HT

To 15 grams CYCLOTENE 4026-46 was added 0.77 gram of R45HT. A 0.3 weightpercent partially hydrolyzed vinyl triacetate silane solution wasapplied to a 4 inch silicone wafer as adhesion promoter. The CYCLOTENE4026 solution with R45HT was spread at 500 rpm followed by spin-coatingat 2700 rpm for 30 seconds. The wafer was prebaked at 85° C. for 90seconds on a hot plate. A Karl Suss photo exposure tool was used withthe gap between the wafer and the mask to be 10 μm. The exposure dosewas 600 mJ/cm². The predevelopment bake was 50° C. for 30 seconds. Thewafer was puddle developed with DS-2100. The development time was 22seconds. The wafer was cured and then treated with plasma. Final filmthickness was 10.3 μm. The shape of the vias was distorted. Cracks wereobserved around the vias.

Example 13 Patterning Thin Film of BCB with 10% VECTOR 6241

To 100 grams CYCLOTENE 4026-46 was added 5.13 grams of VECTOR 6241dissolved in 9.2 grams of mesitylene. A 0.3 weight percent partiallyhydrolyzed vinyl triacetate silane solution was applied to a 4 inchsilicone wafer as adhesion promoter. The CYCLOTENE 4026 solution withVECTOR 6241 was spread at 500 rpm followed by spin-coating at 2500 rpmfor 30 seconds. The wafer was prebaked at 85° C. for 90 seconds on a hotplate. A Karl Suss photo exposure tool was used with the gap between thewafer and the mask to be 10 μm. Exposure dose was 600 mJ/cm².Predevelopment bake was 50° C. for 30 seconds. The wafer was puddledeveloped with DS-2100. The development time was 34 seconds. The filmbecame hazy after development. The wafer was cured and then treated withplasma. The final thickness of the hazy film was 7.6 μm.

Example 14 Tensile Properties of BCB with VECTOR 8508, R45HT and BAC-45

Strips of BCB with 5% and 10% VECTOR 8508, R45HT, and BAC-45 weregenerated and tested according to the procedure described by J. Im, etal. at 2^(nd) International Symposium of Advanced Packaging Materials inAtlanta, Ga, March 1996. The results are shown in the table below.

TABLE VI Tensile Properties of BCB with VECTOR 8508, R45HT and BAC-45Elastomer in Elastomer Tensile BCB Content Modulus (Gpa) Strength (Mpa)Strain (%) VECTOR 8508  5% 2.6 81 7.5 10% 2.6 89 12.5 R45HT  5% 2.7 8511.0 10% 2.5 77 8.5 BAC-45  5% 2.7 94 13.5 10% 2.4 90 18.0

Example 15

A solution from 2.08 grams VECTOR 8508 SBS triblock copolymer wasdissolved in 4 grams of mesitylene and 100 grams of B-staged BCB with Mwof 140,000 g/mol. and consisted of 50.9 weight percent BCB in mesityleneand was made photosensitive by using BAC-E (defined on p. 8) (1.85grams, 3.5 weight percent) as photo cross-linker. To a 4 inch diameterwafer was applied a 0.3 weight percent partially hydrolyzed vinyltriacetate silane as adhesion promoter. BCB photo formulation was spreadat 500 rpm for 10 seconds followed by spin-coating at 5000 rpm for 30seconds. The wafer was prebaked on a hot plate at 90° C. for 90 seconds.A Karl Suss photo exposure tool was used and the gap between the waferand the mask was 10 μm. The exposure dose was 413 mJ/cm². The wafer waspuddle developed with DS 2100. Development time was 156 seconds. Thedeveloped wafer was baked on a hot plate at 90° C. for 90 seconds beforeit was cured at 250° C. under nitrogen. The cured wafer was treated withplasma for 45 seconds. Final film thickness was 10.5 μm. The thicknessafter bake was 12.7 μm. The film retention was 83%. All 50 μm vias wereopen with bottom of via at 38 to 41 μm.

Example 16

VECTOR 8508 SBS (2.1 grams), DVS-bisBCB monomer (52.9 grams) andmesitylene (145 grams) were heated at 165° C. under nitrogen until Mw ofBCB reached 83,000 g/mol. Mw was measured by GPC. Measurement includedBCB and SBS. The solution was filtered with 1 μm filter and concentratedto 39% by weight of BCB. BAC-E (283 mg, 3.5 wt. percent) was added to 20grams of the BCB/SBS rubber solution. A 0.3 weight percent partiallyhydrolyzed vinyl triacetate silane was applied to a 4 inch wafer asadhesion promoter. BCB/SBS rubber/BAC-E solution was spread at 500 rpmfollowed by spin-coating at 2000 rpm for 30 seconds. The wafer wasprebaked at 90° C. for 90 seconds on a hot plate. A Karl Suss photoexposure tool was used with the gap between the wafer and the mask to be10 μm. The exposure dose was 1000 mJ/cm². The wafer was puddle developedwith DS-2100. Development time was 73 seconds. The developed wafer wasbaked on a hot plate at 90° C. for 90 seconds before it was cured at250° C. under nitrogen. The cured wafer was treated with plasma for 30seconds. The final film thickness was 9 μm. Film thickness after bakewas 11 μm. Film retention was 82%. All 75 μm vias were open.

What is claimed is:
 1. A curable composition comprising: a) at least oneprecursor compound selected from arylcyclobutene monomers,arylcyclobutene oligomers, and combinations thereof; and b) a polymer oroligomer having a backbone comprising ethylenic unsaturation andterminal acrylate or methacrylate groups.
 2. The composition of claim 1wherein the ethylenically unsaturated polymer or oligomer is apolybutadiene.
 3. The composition of claim 1 further comprising across-linking aid and an antioxidant.
 4. An article comprising a metalfoil and on that metal foil a layer of the composition of claim
 1. 5.The article of claim 4 wherein the metal foil is copper.
 6. The curedreaction product of the composition of claim
 1. 7. A photoimageablecomposition comprising (a) at least one precursor compound selected fromarylcyclobutene monomers, arylcyclobutene oligomers, and combinationsthereof; (b) a polymer or oligomer having a backbone comprisingethylenic unsaturation; and (c) a photoactive compound selected from thegroup consisting of azides, bismaleimides, acrylates, acetylenes,isocyanates, aromatic ketones such as 2,2-dimethoxy-2-phenylacetophenone, conjugated aromatic ketones, and benzophenone-containingpolymers.